Dumbbell base



FIG. 1 is a top perspective view of a dumbbell base.

FIG. 2 is a side elevational view of the dumbell base, the opposite side being a mirror image thereof.

FIG. 3 is an end elevational view of the dumbbell base, the opposite end being a mirror image thereof.

FIG. 4 is a top plan view of the dumbell base; and,

FIG. 5 is a bottom view of the dumbell base.

The broken lines illustrate portions of the Dumbbell Base which form no part of the claimed design. 

The ornamental design for a dumbbell base, as shown and described. 